Here's some tips regarding the L2 Algae Scrubber:
Just a few common questions that I have answered for some, as well as a few tips/etc.
1) Stand-off screws: The scrubber is packed with the stand-off screws all the way in. Back them out so that when you look down the back of the heat sink (through the fins) you see the point of the screw sticking out a little, maybe 1/8" or so. This should position the heads of the screws such that the LEDs will be plenty clear of the diffuser plate.
2) Installing the diffuser: I put the diffuser in smooth side to the window, bumpy side toward the LEDs. This is how this material is used in light fixtures in the ceiling, and that's how it is supposed to be - so just leave them as-is.
3) Installing/removing the Heat Sink: The heat sinks are packed in the locations where they should be used; the wiring connections should be opposite of the inlet and emergency drain side. Insert the heat sink starting at an angle with the top tilted out and screws touching/close to the diffuser, then tip it in. Remove by tipping the top edge outward.
4) Thumbscrews: Once the heat sink is all the way in, insert the thumbscrews into the threaded holes on the drain side. The screws should be snug, but not so tight that you start to bend the acrylic outward more than 1/16" (don't crank them down with a wrench or anything!) These are meant just to keep the heatsink from falling out if you tip the device a little too much or bump it, etc.
5) LED power connections: The fixtures connect to each other, then the remaining leads to the driver. Each fixture has a male and female plug. On the LED side, both red wires have the same connector, and both black wires have the opposite connector. The connectors on the driver wires are such that you can only plug the red to one of the reds (doesn't matter which) and black to black. The interconnection between the 2 fixtures is red to black; it doesn't matter which 'order' you follow. So connect Driver Red to one of the Red leads on one of the fixtures, then the Black from that fixture to the Red on the other fixture, and the last Black to Driver Black. I shouldn't say that you cannot connect it wrong, but you would have to try really hard to connect it wrong.
6) Slot pipe & screen: Insert the screen all the way into the pipe, poke the beaded cable tie through a hole near the center of the first fully exposed row, and pull it through roughly halfway or really wherever you want. I usually cut the tie so that you can pull 2 beads through the hole and slide it to the locked position. This way it doesn't get in the way of the lid or anything. If you use the same hole every time, it will get easier to push it through. You can also cut one of the vertical members away and then it's really easy all the time. I always remove the tie and scrub the smooth area of the screen to keep it clear. The rough area starts at the second row down from the slot.
7) Slot tube connections: Probably preaching to the choir here but wrap the threaded connector on the pipe with Teflon tape a few times and screw into the union. I tend to use the side of the union with the washer on it on the pipe side, but you have to make sure that washer doesn't fall off and go down the drain when you're cleaning the slot. I lost one in the lawn one time. Not fun. Anyways, same deal on the other side, wrap the thread-to-hose-barb threading and screw into the other side of the union.
8) Connection to pump/overflow: the hose barb that comes with the unit is for 5/8" ID hose. I use 5/8" ID / 3/4" OD stuff from anywhere. This hose size matches the outlet of the Eheim Compact 1000 pump, which is why I chose it. Use whatever size you want if you feed via overflow or your own pump. Larger diameter hose will allow for slightly more flow, but with a short run it won't make a huge difference. If you're using the Eheim pump, I recommend that you use a hose clamp or zip-tie over the hose at the pump.
9) Screen hanging: When you put it all together, try to make sure the screen is hanging as close to vertical as possible. If the pipe is rotated too much, the flow will be cut off on one side of the screen. That's nothing specific to this scrubber, that's always been the case - just worth mentioning.
10) Drain: if you don't screw anything into the bulkhead, the outflow water from the bottom drain is going to splash all over the place. So you probably want to get a screw-in adapter and a short section of pipe so that the drain is just below the operating water level in your tank/sump.
11) Emergency Drain: Add a section of 1" PVC into the eblow (friction fit is fine, as lone as it's snug) to a point above the operating water level. You want to hear noise when water runs through this so that you know something is wrong. If you plumb it below water level, drill an air relief hole above the water level so that the pipe doesn't get airlocked and cause the scrubber to overflow. Because that would be bad.
12) Silent and bubble-free operation: I will admit that I haven't had time to mess with this since I figured it out, so y'all can be my involuntary testing group LOL. Here it is, (sort of) simplified: The key to making the drain silent is "tuning" the pipe so that it flows at the same approximate rate as the pump/overflow supplies. This is similar to a "Herbie" or "BeanAnimal" full-siphon overflow system, sort of. When the bottom of the drain pipe is submerged, the drain has a maximum flow rate that is based on vertical drop out of the drain. The higher above the sump/tank operating water level, the higher this maximum flow rate. At 210 GPH, that drain is well below the maximum with zero vertical drop, so it's going to suck air into the drain and gurgle. To solve this (if it's too noisy for your liking, or bubbles are causing you headaches) then you place a ball valve or gate valve on the drain and adjust it so that the bubbles stop flowing out of the drain. That's it. If you close the valve too much, the scrubber chamber will start to fill up until either the extra pressure from the rising water column increases the flow through the drain and it 'balances', or if it's closed too much, the water will fill the box and start to flow through the emergency drain. You should be able to adjust the valve so that the water doesn't rise above the false bottom on the ends of the box on the inside. You can do that with any size valve. The drain bulkhead is 1" threaded on the inside, and you can get a reducer down to 3/4" and put a 3/4" valve on it. Note that you can only really use this technique on this scrubber because of the secondary drain. If you get an algae detachment, it could clog the drain, so if you run it like this, it would be wise to check the scrubber every couple days to make sure the water level is still correct. Also, as with any plumbing, the inside of new pipes will gradually form a slime coating and the flow rate will likely change over the first few weeks to months. So you will probably need to make adjustments to the ball/gate valve. if you use a ball valve, it helps to get some silicone grease and smear it on the ball with the valve closed, then open and close it a bunch to lubricate it so that fine adjustments are easier. Gate valves are easier to adjust but a little more expensive (I think).
13) Removing the screen for cleaning: If you have headroom above the unit to lift the screen out, then what I would do after shutting off the flow and unscrewing the union is use underside of the lid to catch the water dripping off the screen as you remove it clear of the scrubber box. Lift the screen up an inch or so to let the excess water drain (tilt it slightly), flip the lid over, and lift the screen up and move the lid under the bottom edge, then move the screen/lid toward the pump/emergency drain side to get clear of the scrubber. Avoid moving the dripping screen over the heat sinks. There is very little chance that if you dripped water onto the top that it would find it's way to the LEDs, but why tempt fate?
14) LED On/off time: there is enough light on the screen such that you only need to run the light half of the 'standard' hours. So 9 hours on, 15 hours off. I would not run the lights any longer than 9 hours, especially when starting up the screen. The screen will typically fill in from the outside in. This is because the 3 LEDs in the middle concentrate the intensity and it kind of overpowers the algae at first.
15) Curing period: this typically takes 4-6 weeks, but depends on tank conditions. The screen won't grow much if you don't have livestock in the tank, or at least some source of waste, and urea from live animals is the best source of food for algae. This is what I recommend for cleaning:
A) First cleaning at 7 to 14 days: run under slow running tepid water, at the MOST, just rub the screen lightly with tips of fingers.
B) 2nd to 3rd or 4th cleaning, same as above, every 7 to 10 days
C) when you get strands of algae that are to attached to rub off, then you can start using the back of your fingernails.
D) when you can't scrape them off with your fingernails, switch to a plastic pot scraper, credit card or something like a Kent acrylic scraper blade
E) always make sure the top inch of the screen is clean by scrubbing with a toothbrush
F) always scrub the slot with a toothbrush
G) remove the false bottom and scrub with toothbrush
H) if you don't clean the inner chamber of the box each week, at least check it for buildup, and clean it about once a month (false bottom should collect most of the buildup of algae, which reduces the need for weekly thorough cleaning)
I) Clean algae off the inside of the windows with a soft toothbrush or non-abrasive cloth (most paper towels will scratch acrylic)
J) When flow is off, water will remain in the bottom of the box. Sometimes you will get some algae that breaks away when you pull out the screen, and this will get flushed down the drain if you don't suck it out with a turkey baster before putting everything back together